title: The importance of social condition in the hormonal and behavioral responses to an acute social stressor in the male Siberian dwarf hamster (Phodopus sungorus).
abstract: Social condition is an important factor in determining the behavioral and hormonal responses to a social stressor in the Siberian dwarf hamster (Phodopus sungorus). We predict that males housed with a female or a family (female and pups) will show an increase in the magnitude of the behavioral and hormonal responses to a male intruder compared to those of individually housed males. Three treatment groups were studied: individually housed males that had been previously group-housed in same-sex colonies (males, n = 10), males housed with a female (male + female, n = 9), and males housed with their female and pups (male + family, n = 12). Males were monitored for aggressive behavior toward an intruder male for 10 min. Blood samples were taken at baseline and after the encounter. Male + female and male + family groups spent more time in aggressive behavior (P < 0.05), such as attacking (P < 0.05) and fighting (P < 0.05), than did individually housed males. These same groups showed significant increases in plasma cortisol after the encounter (P < 0.01) whereas there were no significant increases in plasma cortisol in solitary males. All groups showed significantly lower levels of plasma testosterone (male, P < 0.001, male + female, P < 0.05; male + family, P < 0.01) whereas a significant increase in prolactin occurred only in the male + family group (P < 0.05). There was a significant positive correlation between postencounter cortisol levels and total number of minutes spent in aggressive behavior (P < 0.05). These results demonstrate that the introduction of a novel intruder male results in an activation of the hypothalamic-pituitary-adrenocortical axis and a suppression of the reproductive axis. Furthermore, pairing of a male with a female alters the behavioral and hormonal responses to an intruder male.
authors.affiliation: Department of Zoology, Arizona State University, Tempe 85287, USA.
authors.forename: W L
authors.initials: WL
authors.lastname: Castro
authors.forename: K S
authors.initials: KS
authors.lastname: Matt
mesh_terms: D000374:Aggression / Q000502:physiology; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D006224:Cricetinae; D005260:Female; D006120:Grooming; D006728:Hormones / Q000097:blood*; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D017111:Phodopus; D011388:Prolactin / Q000097:blood; D012931:Social Environment; D013315:Stress, Psychological / Q000097:blood / Q000503:physiopathology*
chemical_list: D006728:Hormones; D011388:Prolactin; D006854:Hydrocortisone